This multidisciplinary investigation continues into adulthood a longitudinal study of 38 individuals with sex chromosome abnormalities (SCA) who have been followed since birth. Identified through the chromosome screening of 40,000 consecutive newborn, this cohort is free of the selection bias characteristic of clinically identified propositi. Controls will include 25 siblings of the propositi. All subjects will be seen annually over a period of four years. The long-term objective of this project has been to establish the phenotype and developmental prognosis of SCA children, adolescents, and adults. Building upon our previous findings of karyotype-specific learning, motor, language, behavioral, and endocrine problems, this protocol targets four assessment areas in adulthood: 1) brain structure, which our pilot study indicates is altered by SCA; 2) language abilities, specifically verbal fluency, phonologic awareness, reading, and auditory short-term memory, believed to be influenced by SCA; 3) psychosocial adaptation, diminished in many SCA children and adolescents and most pathological in 47, XXX young women; and 4) physical and endocrine problems, seen in some propositi relationships is planned to determine sources of resilience in propositi with normal development and strong adaption. Results from the study are used both in the genetic counseling of parents of a prenatally diagnosed SCA fetus and to provide guidance to SCA patients and their families. No similar data on SCA adult adaptation is available. This is one of only two studies in the world continuing to follow an unselected cohort of SCA propositi, and it is unlikely that any such study will be initiated again in the foreseeable future.